1. Field
Example embodiments relate to semiconductor chips, and for example, to a semiconductor chip supplied with drive voltages by a power gating scheme.
2. Description of Related Art
Semiconductor chips are supplied with drive voltages by means of power gating schemes in order to reduce power leakage consumption. A time for stabilizing an operation after entering into a normal operation mode from a sleep mode in a semiconductor chip is called wake-up latency. In other words, wake-up latency means a time taken by each internal node of the semiconductor chip to arrive at a stable voltage, for example, a time for turning a gate-source voltage (VGS) of a power gating transistor into an operation voltage. The semiconductor chip does not begin any operation until each internal node reaches the stable voltage.
In a conventional semiconductor chip, a power gating operation is conducted to supply drive voltage into blocks by switching power gating transistors in the semiconductor chip. However, internal blocks of the semiconductor chip are different from each other in wake-up latency, e.g., a time for arriving at a stable voltage may differ between internal blocks. The internal blocks of the semiconductor chip have different wake-up latency because the internal blocks are different from each other in a current amount required for charging the stable voltage, but the same in current path, i.e., the same power gating transistor. For example, an internal block, which includes denser and more complicated logic circuits, e.g., arithmetic units, consumes more current than other internal blocks that are relatively less dense in circuit structure.
FIG. 1 shows an example graph illustrating a time gap among blocks of a semiconductor chip in arriving at a stable voltage. Referring to FIG. 1, a relatively less dense block represented by reference VDDmin operates in a shorter wake-up time (or latency) T1, while a relatively denser and more complicated block represented by reference VDDmax operates in a longer wake-up time T2. Because the semiconductor chip does not operate until all of internal circuit blocks are charged up to the stable voltage, a wake-up time of the semiconductor chip is dependent on the wake-up time T2 of the denser and more complicated block that arrives at the stable voltage in the longer time. For example, a conventional semiconductor chip has to wait until the internal block having the longest wake-up time reaches a stable voltage in order to set up a normal operating condition.